War crimes in World War I

During World War I (1914–1918), belligerents from both the Allied Powers and Central Powers violated international criminal law, committing numerous war crimes. This includes the use of indiscriminate violence and massacres against civilians, torture, sexual violence, forced deportation and population transfer, death marches, the use of chemical weapons and the targeting of medical facilities.

Collective punishment and massacres of Serbs by Austria-Hungary
During the first invasion of Serbia in 1914, Austro-Hungarian forces occupied parts of the country for 13 days. Their war aims were not only to eliminate Serbia as a threat, but also to punish her for fuelling South Slav irredentism in the empire. The occupation turned into a war of annihilation, accompanied by massacres of civilians and the taking of hostages. Austro-Hungarian troops committed a number of war crimes against the Serbs, especially in the area of Mačva, where according to historian Geoffrey Wawro, the Austro-Hungarian army subjected the civilian population to a wave of atrocities. During this short occupation, between 3,500 and 4,000 Serb civilians were killed in executions and acts of random violence by marauding troops.Mass killings took place in numerous towns in northern Serbia. On 17 August 1914, in Šabac, 120 residents—mostly women, children and old men—were shot and buried in a churchyard by Austro-Hungarian troops on the orders of Feldmarschall-Leutnant Kasimir von Lütgendorf. The remaining residents were beaten to death, hanged, stabbed, mutilated or burned alive. A pit was later discovered in the village of Lešnica containing 109 dead peasants who were "bound together with a rope and encircled by wire"; they had been shot and immediately buried, even with some still alive. A claim from a local spy that "traitors" were hiding in a certain house was enough to sentence the whole family to death by hanging. Priests were often hanged, under the accusation of spreading the spirit of treason among the people. Victims were usually hanged on the main squares of villages and towns, in full view of the general population. The lifeless bodies were left to hang by the noose for several days as an act of intimidation.

Austria's propaganda machinery spread anti-Serb sentiment with the slogan "Serbien muss sterbien" (Serbia must die). During the war, Austro-Hungarian officers in Serbia ordered troops to "exterminate and burn everything that is Serbian", and hangings and mass shootings were everyday occurrences. Austrian historian Anton Holzer wrote that the Austro-Hungarian army carried out "countless and systematic massacres…against the Serbian population. The soldiers invaded villages and rounded up unarmed men, women and children. They were either shot dead, bayoneted to death or hanged. The victims were locked into barns and burned alive. Women were sent up to the front lines and mass-raped. The inhabitants of whole villages were taken as hostages, humiliated and tortured." Multiple source state that 30,000 Serbs, mostly civilians, were executed by Austro-Hungarian forces by the end of 1914.

Forced displacement and starvation of Serbs
After being occupied completely in early 1916, both Austria-Hungary and Bulgaria announced that Serbia had ceased to exist as a political entity, and that its inhabitants could therefore not invoke the international rules of war dictating the treatment of civilians as defined by the Geneva Conventions and the Hague Conventions.

The Military General Governorate of Serbia (MGG/S), as well as the High Command in Vienna, considered sending civilian prisoners to internment camps. During the occupation, between 150,000 and 200,000 men, women and children were deported to various camps in Austria-Hungary; it has been estimated they represented slightly more than 10 per cent of the Serb population. Since Serbia did not have its own Red Cross, Serbian prisoners did not have access to the aid the Red Cross provided to other Allied prisoners. Moreover, Serbian prisoners were not considered "enemy aliens" but "internal enemies" by Austria-Hungary's Ministry of War. By defining them as "terrorists" or "insurgents", the Austro-Hungarian authorities were not obliged to disclose the number of captives they held, and which camps they were being held in, to Red Cross societies.

Serbs also suffered from famine; General Franz Conrad von Hötzendorf gave orders for Serbia's resources be "squeezed dry" regardless of the consequences for the population. Looting by occupying soldiers, combined with the food exporting policies of Austria and Germany, caused mass starvation, leading to the deaths of 8,000 Serbians during the winter of 1916. According to a Red Cross report dated 1 February 1918, by the end of 1917, there were 206,500 prisoners of war and internees from Serbia in Austro-Hungarian and German camps. According to the historian Alan Kramer, the Serbians in Austro-Hungarian captivity received the worst treatment of all the prisoners, and at least 30,000–40,000 had died of starvation by January 1918.

Thalerhof Internment Camp
Austrian authorities interned civilians from the province of Galicia and sent them to internment camps, on charges of being part of the Galician Russophilia movement.

Baralong incidents
On 19 August 1915, the German submarine U-27 was sunk by the British Q-ship HMS Baralong. All German survivors were summarily executed by Baralong's crew on the orders of Lieutenant Godfrey Herbert, the captain of the ship. The shooting was reported to the media by American citizens who were on board the Nicosia, a British freighter loaded with war supplies, which was stopped by U-27 just minutes before the incident.

On 24 September, Baralong destroyed U-41, which was in the process of sinking the cargo ship Urbino. According to a survivor from the submarine, Baralong continued to fly the US flag after firing on U-41 and then rammed the lifeboat carrying the German survivors, sinking it.

Blockade of Germany
After the war, the German government claimed that approximately 763,000 German civilians died from starvation and disease during the war because of the Allied blockade. An academic study done in 1928 put the death toll at 424,000. Germany protested that the Allies had used starvation as a weapon of war. Sally Marks argued that the German accounts of a hunger blockade are a "myth", as Germany did not face the starvation level of Belgium and the regions of Poland and northern France that it occupied. According to the British judge and legal philosopher Patrick Devlin, "The War Orders given by the Admiralty on 26 August [1914] were clear enough. All food consigned to Germany through neutral ports was to be captured and all food consigned to Rotterdam was to be presumed consigned to Germany." According to Devlin, this was a serious breach of international law, equivalent to German minelaying. The blockade was maintained for eight months after the armistice in November 1918, into the following year of 1919. Foodstuffs imports into Germany continued to be controlled by the Allies until German authorities signed the Treaty of Versailles in June 1919. In March 1919, Winston Churchill informed the House of Commons, that the ongoing blockade was a success and "Germany is very near starvation." From January 1919 to March 1919, Germany refused to agree to Allied demands that it surrender its merchant ships to Allied ports to transport food supplies. Some Germans considered the armistice to be a temporary cessation of the war and knew, if fighting broke out again, their ships would be seized. Over the winter of 1919, the situation became desperate and Germany finally agreed to surrender its fleet in March. The Allies then allowed for the import of 270,000 tons of foodstuffs.

Both German and non-German observers have argued that these were the most devastating months of the blockade for German civilians, though disagreement persists as to the extent and who is truly at fault. According to Max Rubner, 100,000 German civilians died due to the continued blockade after the armistice. In the UK, Labour Party member and anti-war activist Robert Smillie issued a statement in June 1919 condemning continuation of the blockade, claiming 100,000 German civilians had died as a result.

Bulgarian massacres of Serbs
Bulgarian Tsar Ferdinand declared on the eve of war: "the purpose of my life is the destruction of Serbia". Many Bulgarian troops were side-lined from front line duty to take part in the occupation of Serbia, past animosities led to brutality, the local population was left a choice between Bulgarisation or being subject to violence, large scale deportations and the treatment of the residents of the occupation zones came close to genocidal actions. The Documents relatifs aux violations des Conventions de La Haye et du Droit international, commis de 1915–1918 par les Bulgares en Serbie occupée, a report covering alleged atrocities committed in Serbia, published after the war, stated that ‘anyone unwilling to submit him or herself to the occupiers and become Bulgarian was tortured, raped, interned, and killed in particularly gruesome manners, some of which recorded photographically'. Bulgarian units that occupied Serbian territories showed extreme brutality, systematically expelling the non-Bulgarian population in the regions they occupied, they arrested the population and set the rebel villages on fire.

In addition to the numerous cases of rape, Bulgarian forces encouraged the mixed marriage of Serbian women with Bulgarian men and espoused the view that children born to such marriages should be raised as Bulgarians. Middle-class Serbian functionaries were also suppressed: teachers, religious workers, functionaries, and intellectuals were executed by the Bulgarian soldiers who were following strict instructions to treat civilians the same way they treated soldiers. Additionally, there were regular bombardments of Serbian territories by the aviation and Bulgarian artillery which were operating on the Balkan front around the end of 1916. At the same time, there was a prohibition of Serbian culture; Bulgarians systematically looted Serbian monasteries and the toponymy of villages was changed to Bulgarian.

In addition to those sent to concentration camps, some 30,000 Serbs were sent to Austrian camps or used as forced labour. Factories were plundered of their machinery and a devastating typhus epidemic stalked the land. Thousands died in desperate uprisings, and in some cases, Bulgarian policy was so rigid that it even provoked mutinies among its own soldiers. The Bulgarian soldiers are depicted as simply living off the land without paying any redistribution and also robbing and hitting civilians, whereas the peasants had to work for the occupational authorities without getting any pay, this sometimes included working on defensive positions and carrying ammunition for the Bulgarians which violated the Hague conventions. In ex-Serb Macedonia, for the first time in history, gas chambers were used for the purpose of mass executions, exhaust pipes of trucks were attached to sealed sheds by Bulgarian soldiers where they herded the Serbs whom they wished to eliminate.

Bombardment of English coastal towns
On 16 December 1914, the Imperial German Navy launched a raid on the British seaport towns of Scarborough, Hartlepool, West Hartlepool, and Whitby. The attack resulted in 137 fatalities and 592 casualties. The raid was in violation of the ninth section of the 1907 Hague Convention which prohibited naval bombardments of undefended towns without warning, because only Hartlepool was protected by shore batteries. Germany was a signatory of the 1907 Hague Convention.

Indiscriminate attacks in German-occupied territory
In response to actions by Russian prisoners (many of whom tried to sabotage German plans and kill German soldiers), Germany resorted to harsh pacification measures and terror actions, including brutal reprisals against civilians. Before long, similar practices were instituted throughout the Eastern and Western areas of German occupied territory.

Rape of Belgium
The Imperial German Army ignored many of the commonly-understood European conventions of war when between August and October 1914, some 6,500 French and Belgian citizens were murdered, often in near-random, large-scale shootings ordered by junior German officers. On some occasions, attacks against German infantry positions and patrols that may have actually been attributable to "friendly fire" were blamed on francs-tireurs (guerrillas), who were regarded as bandits and outside the rules of war, eliciting ruthless measures by German forces against the civilians and villages suspected of harboring them. In addition, they tended to suspect that most civilians were potential francs-tireurs, with German soldiers taking, and sometimes killing, hostages from among the civilian population.

The Germans treated any resistance in Belgium—such as sabotaging rail lines—as illegal and immoral, and shot the offenders and burned buildings in retaliation. The German Army destroyed 15,000–20,000 buildings—most infamously the university library at Leuven—and generated a wave of refugees, numbering at over a million people. Over half the German regiments in Belgium were involved in major incidents. In destroying the Leuven library, Germany violated it's obligation, as a signatory to the 1907 Hague Convention, that "in sieges and bombardment, all necessary steps must be taken to spare, as far as possible, buildings dedicated to religion, art, science, or charitable purposes"; the Treaty of Versailles, one of the treaties that ended the war, included a clause to strengthen the protection of cultural property. Large numbers of cases of rape were also reported.

British propaganda dramatising the Rape of Belgium attracted much attention in the United States, while Berlin said it was both lawful and necessary because of the threat of franc-tireurs like those in France in 1870. The British and French press were mostly factual in their reporting of the atrocities, but wrote about them "in the language of vilification". Thus, as accounts were disseminated at home and in the United States, they played a major role in dissolving support for Germany.

Unrestricted submarine warfare
Unrestricted submarine warfare was instituted in 1915 in response to the British naval blockade of Germany. Germany intended to starve Britain as well, but unlike the British, prize rules, which were codified under the 1907 Hague Convention—such as those that required commerce raiders to warn their targets and allow time for the crew to board lifeboats—were disregarded and commercial vessels were sunk regardless of nationality, cargo, or destination. Following the sinking of the RMS Lusitania on 7 May 1915 and subsequent public outcry in various neutral countries, including the United States, the practice was withdrawn. However, Germany resumed the practice on 1 February 1917 and declared that all merchant ships regardless of nationalities would be sunk without warning. This outraged the U.S. public, prompting the U.S. to break diplomatic relations with Germany two days later, and, along with the Zimmermann Telegram, led the U.S. entry into the war two months later on the side of the Allied Powers. Around 15,000 British civilian sailors were killed in the submarine campaign, with a smaller number from other states.

While the German attempt at a blockade was much less successful in terms of inflicting civilian suffering, during the war and prior to World War II, Germany's actions were widely considered to be a greater war crime, and are technically still illegal today.

Torpedoing of HMHS Llandovery Castle
The Canadian hospital ship was torpedoed by the German submarine SM U-86 on 27 June 1918 in violation of international law. Only 24 of the 258 medical personnel, patients, and crew survived. Survivors reported that the U-boat surfaced and ran down the lifeboats, machine-gunning survivors in the water. The U-boat captain, Helmut Brümmer-Patzig, was charged with war crimes in Germany following the war, but escaped prosecution by going to the Free City of Danzig, beyond the jurisdiction of German courts.

Japanese war crimes
During the march towards the German port in Tsingtao and the siege that followed, Japanese forces killed 98 Chinese civilians and wounded 30; there were also countless incidents of rape against Chinese women committed by Japanese soldiers.

Genocide and ethnic cleansing
In the final years of the Ottoman Empire's existence, the Committee of Union and Progress (CUP) committed a genocide against the empire's Armenian population. The Ottomans carried out organised, systematic massacres and deportations of Armenians throughout the war, and they portrayed acts of resistance by Armenians as rebellions in an attempt to justify their extermination campaign. In early 1915, a number of Armenians volunteered to join the Russian forces, and the Ottoman government used this as a pretext to issue the Tehcir Law (Law on Deportation), which authorised the deportation of Armenians from the Empire's eastern provinces to Syria between 1915 and 1918. The Armenians were intentionally marched to death, and a large number of them were attacked by Ottoman brigands. While the exact number of deaths is unknown, the International Association of Genocide Scholars estimates that 1.5 million Armenians were killed. The government of Turkey has consistently denied the genocide, arguing that those who died were victims of inter-ethnic fighting, famine, or disease during World WarI; these claims are rejected by most historians. Other ethnic groups were also attacked by the Ottoman Empire during this period, including Assyrians and Greeks, and some scholars consider those events different parts of the same policy of extermination. Genocidal policies against Ottoman Greeks were already put in place by the CUP prior to World War I, and continued after the war began. According to a newspaper of the time, in November 1914, Turkish troops destroyed Christian properties and killed several Christians at Trabzon. The CUP officially sanctioned the forceful migration of Greeks into the Anatolian hinterland. In the fall of 1916, with Allied forces advancing towards Anatolia, and Greece being expected to enter the war on the side of the Allies, preparations were made for the deportation of Greeks living in border areas. As such, in March 1917 the population of Ayvalık, a town of c. 30,000 inhabitants on the Aegean coast, was forcibly deported to the interior of Anatolia under the orders of German General Liman von Sanders. The operation included death marches, looting, torture and massacres against the civilian population. between 1914 and 1922, and for the whole of Anatolia, there are academic estimates of a death toll ranging from 300,000 to 750,000. Happening contemporaneously was the Sayfo, a genocide of Assyrian people. In mid-1915, interior minister Talaat Pasha ordered for an ethnic cleansing campaign against the Assyrians of Hakkari, and Ottoman forces proceeded to loot Assyrian villages there and destroy cultural artifacts, taking no prisoners as they did so. Many Assyrians fled to Iran, but after the Ottomans began occupying parts of Iran, Djevdet Bey ordered massacres of Christian civilians to prevent them from joining to fight for Russia. Between February and May (when the Ottoman forces pulled out), there was a campaign of mass execution, looting, kidnapping, and extortion against Christians in Urmia, and Assyrian women were targeted for kidnapping and rape; seventy villages were destroyed. Halil Kut and Djevdet Bey ordered the murder of Armenian and Syriac soldiers serving in the Ottoman army, and several hundred were killed. By 1923, the genocide killed an estimated 250,000 to 275,000 Assyrian Christians (about half of the population).

A policy of deporting Ottoman Kurds from their indigenous lands also began during World War I, under the orders of Talaat Pasha. Although many Kurds were loyal to the empire (with some even supporting the persecution of Christian minorities by the CUP), Turkish authorities nevertheless feared the possibility that they would collaborate with Armenians and Russians to establish their own Kurdish state. In 1916, roughly 300,000 Kurds were deported from Bitlis, Erzurum, Palu and Muş to Konya and Gaziantep during the winter, and most died from famine.

On December 1915, the Ottoman's expelled roughly 6,000 Jews with Russian citizenship in Jaffa to Egypt. As British forces advanced towards Palestine in 1917 (combined with the discovery of Nili, an espionage network of Jews that supported the British and opposed the Armenian genocide),  Ottoman authorities began deporting and expelling people throughout Palestine, targeting Jews in particular. On March 1917, everyone living in Gaza (at the time, a town of 35,000–40,000 people, mostly Arabs) was expelled, and the population would not recover until the 1940s. In March and April, on the orders of Djemal Pasha, 10,000 people from Jaffa (including all 8,000 Jew) were deported, an action that was accompanied by severe violence, starvation, theft, persecution and abuse.

Pogroms
During the war, Russian authorities launched pogroms against German populations in Russian cities, massacred Jews in their towns and villages, and deported 500,000 Jews and 250,000 Germans into the Russian interior. On 11 June 1915, a pogrom began against Germans in Petrograd, with over 500 factories, stores and offices looted and mob violence unleashed against Germans. After the Great Retreat of the Russian army, the Chief of the General Staff Nikolai Yanushkevich, with the full support of the Grand Duke Nicholas, ordered the army to devastate the border territories and expel the "enemy" nations within.

Many pogroms also accompanied the Russian Revolution of 1917 and the ensuing Russian Civil War. 50,000–250,000 civilian Jews were killed in atrocities throughout the former Russian Empire (mostly within the Pale of Settlement in present-day Ukraine). There were an estimated 7–12 million casualties during the Russian Civil War, mostly civilians.

Use of chemical weapons
The German army was the first to successfully deploy chemical weapons during the Second Battle of Ypres (22 April – 25 May 1915), after German scientists working under the direction of Fritz Haber at the Kaiser Wilhelm Institute developed a method to weaponize chlorine. The use of chemical weapons was sanctioned by the German High Command in an effort to force Allied soldiers out of their entrenched positions, complementing rather than supplanting more lethal conventional weapons. In time, chemical weapons were deployed by all major belligerents throughout the war, inflicting approximately 1.3 million casualties, but relatively few fatalities: About 90,000 in total. For example, there were an estimated 186,000 British chemical weapons casualties during the war (80% of which were the result of exposure to the vesicant sulfur mustard, introduced to the battlefield by the Germans in July 1917, which burns the skin at any point of contact and inflicts more severe lung damage than chlorine or phosgene), and up to one-third of American casualties were caused by them. The Russian Army reportedly suffered roughly 500,000 chemical weapon casualties in World WarI. The use of chemical weapons in warfare was in direct violation of the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare, which prohibited their use.

The effect of poison gas was not limited to combatants. Civilians were at risk from the gases as winds blew the poison gases through their towns, and they rarely received warnings or alerts of potential danger. In addition to absent warning systems, civilians often did not have access to effective gas masks. An estimated 100,000–260,000 civilian casualties were caused by chemical weapons during the conflict and tens of thousands more (along with military personnel) died from scarring of the lungs, skin damage, and cerebral damage in the years after the conflict ended. Many commanders on both sides knew such weapons would cause major harm to civilians but nonetheless continued to use them. British Field Marshal Douglas Haig wrote in his diary, "My officers and I were aware that such weapons would cause harm to women and children living in nearby towns, as strong winds were common in the battlefront. However, because the weapon was to be directed against the enemy, none of us were overly concerned at all."

The war damaged the prestige of chemistry in European societies, especially the German variety.

Massacres of Albanians
During the Balkan Wars, Albanians were massacred by members of the Balkan League, mostly by Serbian and Montenegrin forces. These massacres continued during the First World War as foreign armies entered Albania. Bulgarian, Serbian, Montenegrin, and Greek forces committed several atrocities in Albania, during occupation, and in other regions inhabited by Albanians. Many villages were burned and destroyed, leaving 330,000 people without homes by 1915. According to the Committee of Kosovo, 50,000 Albanians were killed by Central Powers affiliated Bulgarian forces and around 200,000 Albanians were killed by Allied affiliated Serbian and Montenegrin forces.

Crimes against humanity and genocide as international crimes
On 24 May 1915, on the initiative of Russia, the Triple Entente—Russia, France, and the United Kingdom—issued a declaration condemning the Ottomans for committing "crimes […] against humanity and civilization" against the Armenians, threatening to hold the perpetrators accountable. Although the phrase "crimes against humanity" had been used prior to this, it was the first time the phrase was used in the context of international diplomacy, and it later became a category of international criminal law after World War II.

Polish-Jewish lawyer Raphael Lemkin, who coined the term genocide in 1944, became interested in the prosecution of war crimes after reading about the 1921 trial of Soghomon Tehlirian for the assassination of Talaat Pasha. Lemkin recognized the fate of the Armenians as one of the most significant genocides in the twentieth century.

Establishment of the Geneva Protocol
The Geneva Protocol, signed by 132 nations on 17 June 1925, was a treaty established to ban the use of chemical and biological weapons during wartime. As stated by Coupland and Leins, "it was fostered in part by a 1918 appeal in which the International Committee of the Red Cross (ICRC) described the use of poisonous gas against soldiers as a barbarous invention which science is bringing to perfection". The Protocol required that all remaining stockpiles of chemical weapons be destroyed. Chemical warfare agents that contained bromine, nitroaromatic, and chlorine were dismantled and destroyed. The destruction and disposal of the chemicals did not consider the long-term and adverse impacts on the environment. Although the Geneva Protocol banned the use of chemical weapons during wartime, the Protocol did not ban the production of chemical weapons. In fact, since the Geneva Protocol, the stockpiling of chemical weapons has continued, and weapons have become more lethal. As a result, the Chemical Weapons Convention (CWC) was drafted in 1993, which prohibits the development, production, stockpiling, and use of chemical weapons. Despite there being an international ban on chemical warfare, the CWC "allows domestic law enforcement agencies of the signing countries to use chemical weapons on their citizens".